15 ischemia injury & infarct2
-
Upload
adam-thompson -
Category
Health & Medicine
-
view
692 -
download
0
description
Transcript of 15 ischemia injury & infarct2
12-Lead 12-Lead ElectrocardiographyElectrocardiography
a comprehensive course
Adam Thompson, EMT-P, A.S.Adam Thompson, EMT-P, A.S.
Ischemia,
Injury, &
Infarct
(Part 2)
Evolution of MI
• Insufficient blood supply to the myocardium.– Ischemia, injury or infarction, or all three.
• The branches of coronary arteries arising from the aortic root are distributed on the epicardial surface of the heart.
• These in turn provide intramural branches that supply the cardiac muscle.
• Myocardial ischemia generally appears first.
Evolution of MI
InfarctionIschemia Injury
Needs O2 Damage from Irreversible lack of O2 damage
Ischemia
• Subendocardial ischemia– Ischemia in this area prolongs local recovery time.
Since repolarization normally proceeds in an epicardial-to-endocardial direction, delayed recovery in the subendocardial region due to ischemia does not reverse the direction of repolarization but merely lengthens it.
Ischemia
• Transmural ischemia
– is said to exist when ischemia extends subepicardially. This process has a more visible effect on recovery of subepicardial cells compared with subendocardial cells. Recovery is more delayed in the subepicardial layers, and the subendocardial muscle fibers seem to recover first.
Ischemia
• Hyperacute T-Waves– Results from subendocardial ischemia– Symmetrical & tall– Wide with blunt peak (unlike Hyperkalemia)– Present for about first 30 min. of AMI
• Inverted T-waves– Results from transmural ischemia
Ischemia
Asymmetrical
Symmetrical
Ischemia
Ischemia-Mimic
Peaked T-Waves
Inverted T-Waves
Hyperkalemia STE-Mimic
Injury
• Injury to the myocardial cells results when the ischemic process is more severe.
• In patients with coronary artery disease, ischemia, injury and myocardial infarction of different areas frequently coexist, producing mixed and complex ECG patterns.
Injury
• ST-Depression– Subendocardial
• ST-Elevation – Subepicardial– Transmural.
Injury
Injury
ST-Depression
ST-Elevation
Injury-Mimic
ST-Elevation
Hyperkalemia STE-Mimic
Infarct
• The term infarction describes necrosis or death of myocardial cells.
• Atherosclerotic heart disease is the most common underlying cause of myocardial infarction.
• The left ventricle is the predominant site for infarction; however, right ventricular infarction occasionally coexists with infarction of the inferior wall of the left ventricle.
Infarct
• During acute myocardial infarction, the central area of necrosis is generally surrounded by an area of injury, which in turn is surrounded by an area of ischemia.
• Various stages of myocardial damage can coexist.
• The distinction between ischemia and necrosis is whether the phenomenon is reversible.
Infarct
• Pathological Q-waves– Wider than 0.04sec / 40ms (1 small box)– Deeper than 25% the height of R-Wave
Part 2
• More up next…